1. Field of the Invention
The present invention relates to a semiconductor device having a plurality of semiconductor chips stacked, and to a fabrication method of such semiconductor device.
2. Description of the Related Art
In the field of semiconductor devices, such as semiconductor memories, semiconductor chip-stacked (multi-chip package) semiconductor devices, where a plurality of semiconductor chips are stacked, are known, in order to increase the capacity of memory and to increase functions. One example of such semiconductor device is disclosed in Japanese Patent Application Kokai (Laid-Open) No. 4-116859 and another example is disclosed in Japanese Patent Application Kokai No. 2000-58743.
FIG. 2 of Japanese Patent Application Kokai No. 4-116859 shows a semiconductor device having first and second semiconductor chips which serve as semiconductor memories. The first and second semiconductor chips are shifted to each other, and stacked on the die pad of the lead frame. In this semiconductor device, the first semiconductor chip is secured on the die pad, and the second semiconductor chip is secured on the first semiconductor chip at a shifted position so as to avoid the electrode pads formed at the edge of the upper surface of the first semiconductor chip. The electrode pads on the upper surface of the first and second semiconductor chips are connected to the external terminals of the lead frame by wires (fine metal lines), and all of these are sealed in by resin.
FIG. 1 of Japanese Patent Application Kokai No. 2000-58743 shows another type of a semiconductor device having a first and second semiconductor chips. The first and second semiconductor chips have roughly the same dimensions. An insulation spacer is located between the first and second semiconductor chips so that wire bonding (wire connection) to electrode pads on the upper face (front face) of the first semiconductor chip hidden under the second semiconductor chip is realized.
As larger capacities are demanded for semiconductor memories, multi-chip packages are required to implement larger capacities with conventional semiconductor chips. If a very large memory capacity is desired, 3, 4 or even a higher number of semiconductor chips must be stacked.
However, if many semiconductor chips are stacked shifted from each other stepwise, like the case of the semiconductor device disclosed in Japanese Patent Application Kokai No. 4-116859, the width of the package becomes wide.
If many semiconductor chips are stacked inserting the insulation spacer between each two semiconductor chips, like the case of the semiconductor device disclosed in Japanese Patent Application Kokai No. 2000-58743, on the other hand, then the height (thickness) of the package becomes high.